RAFT (reversible addition fragmentation chain transfer) polymerization processes have been disclosed for the preparation of low-polydispersity polymers from acrylic, styrenic and selected other vinyl monomers. (WO 98/01478, WO 99/31144 and EP 0 910,587).
Trithiocarbonates have been identified as suitable RAFT agents for polymerizing methacrylates, but commercially attractive methods for their preparation have been lacking. For example, methods that convert a thiol to the corresponding sodium salt typically involve the use of NaH, a hazardous material to handle at large scale. Other methods (e.g., electron transfer alkylation) have been used for trithiocarbonate synthesis, but are unattractive due to low yields and the difficult purification procedures required.
A continuing needs exists for an efficient and scalable process for RAFT agents.